In fabricating an electronic device such as a semiconductor device, there is a case where recesses in a substrate are filled with tungsten. The process of filling the recesses in the substrate with tungsten is performed, for example, in fabricating a three-dimensional NAND type memory device.
For example, there have been known methods of filling recesses with tungsten to prevent occurrence of defects such as voids. These methods include embodiment of the recesses with tungsten and etching of the tungsten. Specifically, these methods include forming a tungsten layer on a surface forming and defining the recesses, etching off regions of the tungsten layer causing defects, and subsequently forming another tungsten layer again.
The known methods described above are inefficient because switching is made between the film formation and the etching. Accordingly, in the process of filling the recesses with tungsten, there is a need for improving efficiency while limiting the occurrence of defects.